One method of controlling the casting process has been the use of an induced electromagnetic (EM) field, rather than a mold with definite walls, to both confine and shape the molten metal or alloy which is being cast. This process utilizes a strong electromagnetic field to counterbalance the metallostatic forces effected by the head of molten metal or alloy.
It has generally been necessary to employ relatively low heads of pressure in the molten metal to minimize the power requirements of the electromagnetic field utilized in such a process. Molten metal or alloy head thus becomes an important parameter to measure, as does any change in head during an electromagnetic casting run. In addition, metal or alloy head control in such a process should be sufficiently precise to minimize fluctuations in the metallostatic forces and prevent surges of high velocity molten metal streams within the casting. Accurate knowledge of the height of the liquid metal head and the position of the liquid-solid interface at the periphery of the casting relative to the inductor in an electromagnetic casting operation can be a useful tool in improving overall performance of such operations. For example, ideally it is desired to maintain the position of the liquid-solid interface at the periphery of the forming ingot at the longitudinal center (magnetic center) of the inductor where the field is greatest. This will counteract the maximum static force which is exhibited in the ingot at this point. In addition, control of the location of the liquid-solid interface is essential in prevention of metal spillout or cold folding. This provides added control in that coolant may be caused to impinge upon the forming ingot at the appropriate elevation.